A Statistical and Data Management Core (hereafter referred to as the Statistical Core) is proposed to: (1) coordinate the collection, entry, and verification of data from new and ongoing studies and to create, update, and maintain the databases containing these data; (2) assist in the design and development of proposed new clinical and laboratory based studies; and (3) perform statistical analyses of data resulting from these studies, refining available statistical tools and writing computer programs to implement the refinements as needed for these analyses. The lead biostatistician and data manager from the ongoing program project are joined by another biostatistician, all providing statistical and database management support that is essential to the success of the Program Project. They will continue to collect, validate, and manage data from diverse laboratory and clinical sources, and maintain them in centralized Statistical Core databases. Analysis data sets will be prepared and statistical analyses designed and conducted in fulfillment of project aims. To facilitate the accomplishment of (1) and (2), several database utilities will be developed to reduce the need for manual key-entry, automate data transfer between existing databases, and enhance database security. A file server will be deployed to facilitate multi-user access to Statistical Core databases. Important components of (2) include conducting power calculations to determine required sample sizes, advising investigators regarding appropriate study designs, and assisting in the development of protocols and forms for data collection. To accomplish (3), the Statistical Core will continue to use existing statistical tools, augmenting them with refinements and extensions as needed for particular applications of the Program Project. Mixed-Effects Models for longitudinal data, approaches to the analysis of interval-censored data, and cost-effectiveness analysis strategies are proposed to address the statistical challenges inherent in Program Project analyses.